Stock-based compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Number of Shares
Beginning balance	4,231,178
Granted	2,028,531
Exercised	(34,223)
Forfeited	(208,489)
Ending balance	6,016,997		4,231,178
Option exercisable	3,043,025
Option unvested	2,973,972
Weighted Averaged Exercise Price
Beginning balance	$ 9.21
Granted	1.65
Exercised	0.10
Forfeited	9.23
Ending balance	6.71		$ 9.21
Option exercisable	8.37
Option unvested	$ 5.00
Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years)	7 years 8 months 12 days		7 years 6 months
Weighted Average Remaining Contractual Term, option exercisable	6 years 6 months
Weighted Average Remaining Contractual Term, option unvested	9 years
Aggregate Intrinsic Value, beginning balance	$ 1,640
Aggregate Intrinsic Value, ending balance	858		$ 1,640
Aggregate Intrinsic Value, option exercisable	856
Aggregate Intrinsic Value, option unvested	$ 2
Fair value per common stock used for calculating intrinsic values	$ 1.34		$ 2.33
Cash received from option exercise under share-based payment arrangements	$ 3	$ 239